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1.
A finite difference method is developed to study, on a two-dimensional model, the acoustic pressure radiated when a thin elastic
plate, clamped at its boundaries, is excited by a turbulent boundary layer.
Consider a homogeneous thin elastic plate clamped at its boundaries and extended to infinity by a plane, perfectly rigid,
baffle. This plate closes a rectangular cavity. Both the cavity and the outside domain contain a perfect fluid. The fluid
in the cavity is at rest. The fluid in the outside domain moves in the direction parallel to the system plate/baffle with
a constant speed. A turbulent boundary layer develops at the interface baffle/plate. The wall pressure fluctuations in this
boundary layer generates a vibration of the plate and an acoustic radiation in the two fluid domains.
Modeling the wall pressure fluctuations spectrum in a turbulent boundary layer developed over a vibrating surface is a very
complex and unresolved task. Ducan and Sirkis [1] proposed a model for the two-way interactions between a membrane and a turbulent
flow of fluid. The excitation of the membrane is modeled by a potential flow randomly perturbed. This potential flow is modified
by the displacement of the membrane. Howe [2] proposed a model for the turbulent wall pressure fluctuations power spectrum
over an elastomeric material. The model presented in this article is based on a hypothesis of one-way interaction between
the flow and the structure: the flow generates wall pressure fluctuations which are at the origin of the vibration of the
plate, but the vibration of the plate does not modify the characteristics of the flow.
A finite difference scheme that incorporates the vibration of the plate and the acoustic pressure inside the fluid cavity
has been developed and coupled with a boundary element method that ensures the outside domain coupling. In this paper, we
focus on the resolution of the coupled vibration/interior acoustic problem. We compare the results obtained with three numerical
methods: (a) a finite difference representation for both the plate displacement and the acoustic pressure inside the cavity;
(b) a coupled method involving a finite difference representation for the displacement of the plate and a boundary element
method for the interior acoustic pressure; (c) a boundary element method for both the vibration of the plate and the interior
acoustic pressure.
A comparison of the numerical results obtained with two models of turbulent wall pressure fluctuations spectrums - the Corcos
model [3] and the Chase model [4] - is proposed. A difference of 20 dB is found in the vibro-acoustic response of the structure.
In [3], this difference is explained by calculating a wavenumber transfer function of the plate. In [6], coupled beam-cavity
modes for similar geometry are calculated by the finite difference method.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Wall pressure fluctuations were measured in relation to the structure of coherent motions of a turbulent boundary layer. Their high and low frequency parts were found to be related with the large scale motions of the outer layer and the bursts in the wall region respectively. Based on the experimental results, a structure model of the coherent motions is presented.This paper was presented at the Ninth symposium on turbulence, University of Missouri-Rolla, October 1–3, 1984 相似文献
3.
A speckle photographic method, which is sensitive to changes of gradients in fluid density, is applied for analyzing a compressible turbulent air flow with density fluctuations. Spatial correlation coefficients, turbulent length scales, and energy spectra are determined under the assumption of homogeneous isotropic turbulence. The experiments are performed in a shock tube where the flow is passed through a turbulence grid. Measurements are taken before and after the turbulent regime interacts with the normal shock wave reflected from the tube's end wall. Amplification of the turbulence intensity by the shock interaction process is verified quantitatively and is shown to be restricted to the lower wave numbers in the spectrum.A version of this paper was presented at the 11th Symposium on Turbulence, University of Missouri-Rolla, Oct. 17–19, 1988.To Professor Dr.-Ing. Klaus Gersten on the occasion of his 60th birthday 相似文献
4.
A.O. Borisyuk 《Journal of Fluids and Structures》2010,26(4):658-674
Wall pressure fluctuations, pt, in rigid and elastic pipes behind a local axisymmetric narrowing are studied. A sharp increase in their rms level in a finite region immediately downstream of the narrowing, leading up to a pronounced maximum upstream of the point of jet reattachment, is found. Approximate estimates both for the distance from the narrowing to the point of maximum rms pressure and for the rms magnitude at this point are obtained. Inspection of the wall pressure power spectrum, P, reveals the presence of low-frequency maxima. The maxima are found to be associated with the large-scale eddies in the regions of separated and reattached flow, and their frequencies are close to the characteristic frequencies of the eddies’ formation. These maxima are the main distinguishing features of the spectrum under investigation compared to the power spectrum of the wall pressure fluctuations in a fully-developed turbulent flow in a pipe without narrowing. A comparative analysis of the data for rigid and elastic pipes shows that changes in the pipe wall bending stiffness cause alterations in the flow structure near the wall and the corresponding redistribution of flow energy among the vortices. This results in an increase in the wall pressure amplitude and the low-frequency level of the wall pressure power spectrum, as well as the appearance of new frequency components in this domain. 相似文献
5.
6.
7.
The effect of an internal turbulent bubbly flow on vibrations of a channel wall is investigated experimentally and theoretically. Our objective is to determine the spectrum and attenuation rate of sound propagating through a bubbly liquid flow in a channel, and connect these features with the vibrations of the channel wall and associated pressure fluctuations. Vibrations of an isolated channel wall and associated wall pressure fluctuations are measured using several accelerometers and pressure transducers at various gas void fractions and characteristic bubble diameters. A waveguide-theory-based model, consisting of a solution to the three-dimensional Helmholtz equation in an infinitely long channel with the effective physical properties of a bubbly liquid is developed to predict the spectral frequencies of the wall vibrations and pressure fluctuations, the corresponding attenuation coefficients and propagation phase speeds. Results show that the presence of bubbles substantially enhances the power spectral density of the channel wall vibrations and wall pressure fluctuations in the 250–1200 Hz range by up to 27 and 26 dB, respectively, and increases their overall rms values by up to 14.1 and 12.7 times, respectively. In the same frequency range, both vibrations and spectral frequencies increase substantially with increasing void fraction and slightly with increasing bubble diameter. Several weaker spectral peaks above that range are also observed. Trends of the frequency and attenuation coefficients of spectral peaks, as well as the phase velocities are well predicted by the model. This agreement confirms that the origin of enhanced vibrations and pressure fluctuations is the excitation of streamwise propagating pressure waves, which are created by the initial acoustic energy generated during bubble formation. 相似文献
8.
Assessment of the organization of a turbulent separated and reattaching flow by measuring wall pressure fluctuations 总被引:2,自引:0,他引:2
The effect of local forcing on the organization of a turbulent separated and reattaching flow was assessed by measuring wall pressure fluctuations. Multi-arrayed microphones were installed on the surface to measure the simultaneous spatial and temporal wall pressure fluctuations. Local forcing at the separation edge was applied to the separated flow over a backward-facing step through a thin slit. The organization of the separated and reattaching flow was found to be greatest at the effective forcing frequency. The flow structure was diagnosed by analyzing several characteristics of the wall pressure fluctuations: the wall pressure fluctuation coefficients, wall pressure spectrum, wavenumber-frequency spectrum, coherence, cross-correlation, and multi-resolution autocorrelations of pressure fluctuations using the maximum overlap discrete wavelet transform and continuous wavelet transform. Features indicative of the amalgamation of vortices under the local forcing were observed; this amalgamation process accounted for the observed reduction of the reattachment length. Examination of the wall pressure fluctuations revealed that introduction of local forcing enhanced flapping motion as well as the streamwise and spanwise dispersions of vortical structures. 相似文献
9.
Near-wall pressure fluctuations in turbulent flows are of considerable interest in many engineering applications. We shall concentrate on a number of specific questions related to the resolution of components of wall pressure spectra. Our emphasis shall be on outstanding problems of turbulent pressure fluctuations in the presence of vibration. A study on the interaction of a transducer with wall vibration resulting from near-wall turbulent flows has been performed. Three methods are described for the study of spectral components of turbulent surface pressure in conditions of flow-induced vibration: the method of separation of turbulent and vibration signals; the method of a vibration-proof turbulent pressure transducer; and a modified method of vibration suppression. A method of low-frequency acoustic-noise suppression is also suggested. 相似文献
10.
激波/湍流边界层干扰问题广泛存在于高速飞行器内外流动中, 激波干扰会导致局部流场出现强压力脉动, 严重影响飞行器气动性能和飞行安全. 为了考察干扰区内脉动压力的统计特性, 对来流马赫数2.25, 激波角33.2°的入射激波与平板湍流边界层相互作用问题进行了直接数值模拟研究. 在对计算结果进行细致验证的基础上, 分析比较了干扰区外层和物面脉动压力的典型统计特征, 如脉动强度、功率谱密度、两点相关和时空关联特性等, 着重探讨了两者的差异及其原因. 研究发现, 激波干扰对外层和物面压力脉动的影响差异显著. 分离区内脉动以低频特征为主, 随后再附区外层压力脉动的峰值频率往高频区偏移, 而物面压力脉动的低频能量仍相对较高. 两点相关结果表明, 外层和物面脉动压力的展向关联性均明显强于其流向, 前者积分尺度过激波急剧增长随后缓慢衰减, 而后者积分尺度整体上呈现逐步增大趋势. 此外, 时空关联分析结果指出, 脉动压力关联系数等值线仍符合经典的椭圆形分布, 干扰区下游压力脉动对流速度将减小, 外层对流速度仍明显高于物面. 相似文献
11.
The shadow and interferometric methods and the laser probe method are used to investigate crossflow past a cylinder on the free-stream Mach number interval M
a
=0.5–1.2 for subcritical Reynolds numbers Re
d
and various initial steam states. Detailed pressure distributions are obtained and the pressure fluctuations on the cylinder surface are measured. The dependence of the Strouhal number on the velocity and thermodynamic parameters of the flow are determined. In single-phase steam flow past a cylinder the greatest fluctuations occur in the separation zone in regimes corresponding to transonic drag crisis. It is shown that spontaneous condensation in the turbulent wake and local supersonic zones may cause an increase in the periodic pressure fluctuations in the separation zone, the maximum increase in the fluctuations being noted when the critical pressure ratio is reached at the rear of the cylinder. The initial wetness of the steam has the greatest effect on the periodic separation characteristics at subsonic flow velocities, and in the case of supersonic flow leads to a substantial increase in the level of the low-frequency pressure fluctuations at the front of the cylinder.(deceased)Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, pp. 118–138, November–December, 1994. 相似文献
12.
A hierarchical structure (HS) analysis (β-test and γ-test) is applied to a fully developed turbulent pipe flow. Velocity signals are measured at two cross sections in the pipe and at a series of radial locations from the pipe wall. Particular attention is paid to the variation of turbulent statistics at wall units 10<y+<3000. It is shown that at all locations the velocity fluctuations satisfy the She–Leveque hierarchical symmetry (Phys. Rev. Lett. 72 (1994) 336). The measured HS parameters, β and γ, are interpreted in terms of the variation of fluid structures. Intense anisotropic fluid structures generated near the wall appear to be more singular than the most intermittent structures in isotropic turbulence and appear to be more outstanding compared to the background fluctuations; this yields a more intermittent velocity signal with smaller γ and β. As turbulence migrates into the logarithmic region, small-scale motions are generated by an energy cascade and large-scale organized structures emerge which are also less singular than the most intermittent structures of isotropic turbulence. At the center, turbulence is nearly isotropic, and β and γ are close to the 1994 She–Leveque predictions. A transition is observed from the logarithmic region to the center in which γ drops and the large-scale organized structures break down. We speculate that it is due to the growing eddy viscosity effects of widely spread turbulent fluctuations in a similar way as in the breakdown of the Taylor vortices in a turbulent Couette–Taylor flow at high Reynolds numbers. 相似文献
13.
A. V. Smol'yakov 《Journal of Applied Mechanics and Technical Physics》1969,10(3):440-444
In this paper we present the results of calculations of the space correlations of the random pressure field which acts on the surface of a flat plate out of a fully developed turbulent boundary layer. Calculations are performed on the basis of available experimental data on the cross-spectral density of the turbulent pressure fluctuations. It is found that the spacetime correlations have an explicitly expressed form similarity. This is used as a basis for deriving a simple approximate relation between the modulus of the normalized cross-spectral density, the energy spectrum, and the maxima of the space-time correlation coefficient. The results of elementary calculations performed on the basis of the obtained relation are shown to be almost identical with those obtained on a digital computer from exact formulas.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, Vol. 10, No. 3, pp. 116–120, May–June, 1969.The author is indebted to Yu. G. Blyudze for useful discussions of the results of this paper. 相似文献
14.
Mahmoud Karimi Paul Croaker Alex Skvortsov Danielle Moreau Nicole Kessissoglou 《国际流体数值方法杂志》2019,90(10):522-543
An efficient hybrid uncorrelated wall plane waves–boundary element method (UWPW-BEM) technique is proposed to predict the flow-induced noise from a structure in low Mach number turbulent flow. Reynolds-averaged Navier-Stokes equations are used to estimate the turbulent boundary layer parameters such as convective velocity, boundary layer thickness, and wall shear stress over the surface of the structure. The spectrum of the wall pressure fluctuations is evaluated from the turbulent boundary layer parameters and by using semi-empirical models from literature. The wall pressure field underneath the turbulent boundary layer is synthesized by realizations of uncorrelated wall plane waves (UWPW). An acoustic BEM solver is then employed to compute the acoustic pressure scattered by the structure from the synthesized wall pressure field. Finally, the acoustic response of the structure in turbulent flow is obtained as an ensemble average of the acoustic pressures due to all realizations of uncorrelated plane waves. To demonstrate the hybrid UWPW-BEM approach, the self-noise generated by a flat plate in turbulent flow with Reynolds number based on chord Rec = 4.9 × 105 is predicted. The results are compared with those obtained from a large eddy simulation (LES)-BEM technique as well as with experimental data from literature. 相似文献
15.
M. L. Ugryumov 《Fluid Dynamics》1987,22(2):211-217
A flow of viscous compressible fluid in the neighborhood of the line of interaction of wall flows is considered. A method of calculating the line of interaction and the direction of the self-induced secondary flow is developed. Papers [1–3] are devoted to the simulation of a separation flow with singularities in the neighborhood of singular lines and points, where boundary-layer equations are invalid. However, the theories of local separation used at present have mainly been developed only for two-dimensional problems, while the models of viscous-inviscid interaction have restrictions in application for turbulent flows with developed separation. The interaction of three-dimensional wall turbulent flows is considered below. It is assumed that the thickness of the boundary layers and the scales of the interaction zones are small in comparison with the characteristic dimension of the system, while the line of discontinuity of the solutions of the three-dimensional boundary layer equations is the same as the line of interaction of the wall flows.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 53–59, March–April, 1987.The author is grateful to G. Yu. Stepanov and V. N. Ershov for their interest in my work and their valuable remarks. 相似文献
16.
This article presents an experimental study of the vibro-acoustic response of a pipe excited by a fully-developed turbulent
air flow. First, the wall pressure field acting on the internal pipe wall is investigated. The power spectral density of the
wall pressure fluctuations is analyzed after cancellation of contaminating background noise. The convection velocity and correlation
lengths are calculated from measured cross-spectra, and the cross-spectra are expressed in Corcos model form. Second, the
vibro-acoustic response of the pipe is analyzed by referring to the structural modes of the pipe.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
S. S. Dmitriev 《Fluid Dynamics》1990,25(6):867-874
The mechanism of turbulent boundary layer separation under the influence of a positive pressure gradient is analyzed. The process of turbulent separation from a smooth wall in a plane diffuser channel has been experimentally investigated. It is shown that separation is determined by the nature of the flow in a certain inner part of the boundary layer, where the friction effect is unimportant. This region of the boundary layer is most exposed to the action of the positive pressure gradient and it is there that the stagnant zone primarily appears.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 69–77, November–December, 1990. 相似文献
18.
Zohreh Mansoori Majid Saffar-Avval Hassan Basirat-Tabrizi Goodarz Ahmadi Santiago Lain 《International Journal of Heat and Fluid Flow》2002,23(6):792-806
A thermo-mechanical turbulence model is developed and used for predicting heat transfer in a gas–solid flow through a vertical pipe with constant wall heat flux. The new four-way interaction model makes use of the thermal kθ–τθ equations, in addition to the hydrodynamic k–τ transport, and accounts for the particle–particle and particle–wall collisions through a Eulerian/Lagrangian formulation. The simulation results indicate that the level of thermal turbulence intensity and the heat transfer are strongly affected by the particle collisions. Inter-particle collisions attenuate the thermal turbulence intensity near the wall but somewhat amplify the temperature fluctuations in the pipe core region. The hydrodynamic-to-thermal times-scale ratio and the turbulent Prandtl number in the region near the wall increase due to the inter-particle collisions. The results also show that the use of a constant or the single-phase gas turbulent Prandtl number produces error in the thermal eddy diffusivity and thermal turbulent intensity fields. Simulation results also indicate that the inter-particle contact heat conduction during collision has no significant effect in the range of Reynolds number and particle diameter studied. 相似文献
19.
A. G. Marchenko 《Journal of Applied Mechanics and Technical Physics》1971,12(3):460-467
The results of an experimental investigation into the steady-state plane turbulent boundary layer in an incompressible liquid at an impermeable wall are presented. Cases of flow at smooth and rough surfaces in the presence of a longitudinal pressure gradient are considered. The results of measurements of the turbulent structure of the flow at various distances from the channel inlet are presented. A detailed analysis of the kinematic and dynamic characteristics of the flow is given. Special attention is paid to the boundary region of the flow close to the wall. A universal law is proposed for the variation in the local resistance coefficient along the boundary layer.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 126–134, May–June, 1971. 相似文献
20.
Sébastien Debert Marc Pachebat Vincent Valeau Yves Gervais 《Experiments in fluids》2011,50(2):339-350
This work illustrates the possibilities of the Ensemble-Empirical-Mode-Decomposition (E-EMD) technique for a detailed analysis
of the time and space characteristics of the wall-pressure fluctuations under a turbulent flow. Pressure fluctuations are
measured with a linear microphone array, for the cases of a turbulent boundary layer and for a diffuse airborne acoustic field.
The E-EMD technique is shown to be an efficient tool for representing the spatial scales of the turbulent fluctuations at
each instant. In particular, this representation is obtained without any particular assumption or a priori information on
the data (e.g. temporal or spatial stationarity of the wall pressure data is not required), and acts, when applied to wide-band
turbulent signals, as a wavenumber filter. Finally, it is shown how, to some extent, the E-EMD technique can separate at each
instant the acoustic (propagative) from the hydrodynamic (convective) energy. 相似文献